A number of processes are known in the art for the production of 2,3-dihydro-2,2-dimethyl-7-benzofuranol.
It is known, for example, to interact o-nitrophenol with metallyl chloride, subsequently effecting the Claisen transposition of the phenolic ether thus obtained, and the further conversion of the nitro group into a hydroxyl group, as disclosed in the U.S. Pat. No. 3,320,286.
Such a process has shortcomings connected with its intricacy and the high costs of the requested raw materials.
Another process comprises the step of interacting catechol with metallyl chloride to give 2-oxymetallylphenol, the latter being subsequently subjected to Claisen transposition, optionally under the influence of acidic catalysts, such as disclosed, for example, in the German Patent Application No. 2,932,458 and the European Published Application No. 40,400. This process mainly exhibits the drawbacks deriving from the low selectivity of the useful reaction product and the high cost of metallyl chloride. Another process consists in reacting catechol with isobutyraldehyde, with the attendant formation of an intermediate, the 2-isopropyl-1,3-benzodioxol, which is subsequently isomerized on a catalyst based on magnesium chloride and palladium on charcoal, such as disclosed, for example, in the U.S. Pat. No. 4,118,400. This process, while providing an acceptable selectivity in the useful reaction product, is unsatisfactory due to its intricacy and the low conversion rating of its second reaction stage.
Therefore, an object of the present invention is to provide a process for the production of 2,3-dihydro-2,2-dimethyl-7-benzofuranol which is exempt, or substantially so, from the above indicated shortcomings.
The process according to the present invention essentially comprises the preliminary reaction between 4-tert.butyl catechol, or catechol, and isobutyraldehyde under the influence of specially provided catalysts and the subsequent contact of the products thus obtained with catalytic amounts of one or more compounds having an acidic nature and an optional final treatment in order to obtain the expected product.